Some light emitting diodes (LEDs) can be fabricated on gallium nitride (GaN) wafers. A conventional GaN LED may emit light when a direct current (DC) voltage is applied in one direction across the LED's terminals (e.g., from the LED's anode to its cathode) but not when the DC voltage is applied in the opposite direction across the LED's terminals (e.g., from the LED's cathode to its anode). DC supply voltages on the order of 3 V-5 V may be sufficient to activate some conventional GaN LEDs. In systems that use conventional GaN LEDs as light sources, a DC supply voltage suitable for activating an LED may be provided by a driving circuit, which can convert an alternating current (AC) supply voltage (e.g., a main AC supply voltage of 110V-240V) into the desired DC supply voltage.